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Microstructural analysis of silicon carbide monofilaments
Author(s) -
Shatwell R. A.,
Dyos K. L.,
Prentice C.,
Ward Y.,
Young R. J.
Publication year - 2001
Publication title -
journal of microscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.569
H-Index - 111
eISSN - 1365-2818
pISSN - 0022-2720
DOI - 10.1046/j.1365-2818.2001.00836.x
Subject(s) - crystallite , raman spectroscopy , materials science , electron microprobe , analytical chemistry (journal) , transmission electron microscopy , microprobe , amorphous solid , scanning electron microscope , raman scattering , microstructure , mineralogy , crystallography , nanotechnology , composite material , optics , chemistry , physics , chromatography , metallurgy
In the development of monofilaments, a good understanding of the process/property relationships is essential. Transmission electron microscopy (TEM) is a powerful tool but too slow and expensive to be used routinely. Alternative, cheaper techniques have therefore been investigated. The microstructures of three SiC monofilaments (DERA Sigma SM1140+, Textron SCS‐6 and Ultra‐SCS) and some experimental samples were studied using a combination of TEM, electron microprobe analysis, Raman microprobe analysis, thermo‐gravimetric analysis (TGA) and differential scanning calorimetry (DSC). It was found that the Raman technique was complementary to TEM and easily identified the presence of amorphous C and Si. These could not be seen by electron or X‐ray diffraction techniques. DSC indicated the presence of free Si in the DERA Sigma SM1140+ monofilament by a distinctive peak at ∼1400 °C. TGA showed the reaction of monofilament components with gaseous species. The Textron SCS‐6 and Ultra species lost weight as C was oxidized to gaseous CO. By contrast, the Sigma monofilament gained weight from formation of SiO 2 from the free Si. The separations of the transverse optical phonon peaks in the Raman spectra were correlated with the density of stacking faults in the SiC crystallites. This was similar in all monofilaments. Analysis of the polarization of the Raman scattering gave information on the orientation of crystallites. The crystallites in SM1140+ and SCS‐6 were orientated predominantly with the <111> parallel to the radius. Preliminary interpretation of the polarized Raman scattering from Ultra‐SCS indicated more than one orientation of crystallite. One possibility was a mixture of <111> and <110> directions parallel to the radius.